276 .KIIIS. BOVE PFTi;HSF.\ 



Oscillatoria formosa Uoiy. 



Gomont, Mono-^r. II ]). 230. \)\. VII. lij^. 16. 



S. Icel. Reykjavik. Laii}^. Tcmp. 35 " ^s 1914. 

 Area: All continents. Anlarctic, Spitzbcrgcn. 



An evidenlly cosmopolilan spcfics which also is l'ouiul uiulcr hij^hly 

 varying condilions. Il occurs in fresh as well as brackish water and 

 has several times been foiind in hol springs at a teni|)erature up lo 

 54 ** C. Borge 1900 p. 11). It secnis also capable oT growing more 

 or less aerophilous in that it is lound on earth (Esniarch 191 1 p. 2(55, 

 Moore and Karrer 1919 p. 304). It probably thrives hest in and on 

 mild. Piepcr (1915 has examined ils movements in connection with 

 the ligilt and finds that it shows positive phototaxis in weak light, ne- 

 gative in strong light. In a certain medium light the Ihreads turn at 

 right angles to the beams of light. In this Pieper sees an adaptation 

 by means of which Ihe algae always can obtain tlu" most favourable 

 illumination. 



Aecording lo Kolkwitz et Marsson (1908 p. 511) il is a-mesosaprobe. 



Oscillatoria numidica Gom. 



Gonionl, Monogr. II p. 231. Guntlier Schmid li) 14 p. 129, fig. 4. 



S. Icel. In stream from Great Geysir, mean lemp. about 40° C. 

 (West 1902 p. 245). 



Area: Kur., Am., Afr. 



This species has only been found five times in all. It was described 

 by Gomont on basis of material from the hot springs at Hammam-Sa- 

 lahin in North Africa. Later il was found by Tilden (1910 p. 81) in a 

 hot-house in Minneapolis, and Gunther Schmid (1914 p. 129, 1917 p. 

 352; found il in similar circumslances in the Hotanical Garden of Jena. 

 Finally it iias been found once more in Minneapolis, bul this time in 

 a small pool with coId water. Judging by the tindings in band it is 

 to be presumed that it is a species which requires a rathcr high tem- 

 perature in order to Ihrive well, bul anylhing definile can of course nol 

 be slated. 



Oscillatoria terebriformis Ag. 



Gomont, Monogr. II p. 234. pi. VII. flg. 24. 



S. Icel. Reykjavik; Laugarne ^^ye 1895 .C. II. ()./! 

 Area: Kur., As., Afr., Anlarctic. 



Coupin (1915 p. 56 considers this species to be a genuine thermal 

 alga. To be true, it has been found several limes in thermae, but just as 

 fre(|uently it has been found in countries where no thermae exist at all, 

 e. g., Denmark. .Swcden. Luxemburg, and even on Hoss Island 'W. and 

 G.S.West 1911 p. 2('>r)) in a pond where the temperature never exceeded 

 60 " F. Therefore I cannol agree with Coupin, l)iit iiiust refer il lo the 

 facultalive thermal algae. 



